Many providers of traditional circuit-switched telephony service, such as AT&T, now offer at least some subscribers the capability to complete voice calls over the Internet. Indeed, the total number of minutes of Voice Over Internet Prtocol (VOIP) calls continues to grow each year because subscribers find such calls more economical by virtue of the fact that such calls often cost less than traditional circuit-switched calls. Unfortunately, the present lack of compatible common gateways has limited deployment of VOIP service. In addition, VOIP telephony does not yet enjoy the reliability of conventional circuit-switched telephony.
In an effort to address the issue of the reliability, U.S. Pat. No. 6,064,727 issued May 16, 2000, to AT&T, the present assignee, proposes a technique for offering a telephone subscriber uninterrupted service by routing a call over an alternate communications channel (e.g., a PSTN link) if call routing cannot occur over a primary communications channel, for example a cable television link. The technique for maintaining uninterrupted telecommunications service disclosed in the '727 patent concerns the availability of the primary communications channel, as well as the characteristics of the call. However, the '727 patent does not address the communications capability of the called party, and in particular, whether the called party has the ability to receive calls over a particular network.
Thus, there is a need for a technique that affords improved reliability while addressing the communications capability of the called party.